1. Field of the Invention
This invention relates to child resistant closures primarily but not exclusively for blister packs for medicaments.
2. Description of the Related Art
Many medicaments are packaged in blister packs comprising a plurality of deformable protrusions formed in a flexible sheet. Unit doses of medicament are received in the protrusions which are sealed by a frangible film. To remove a unit dose, the unit dose is pushed through the frangible film. The arrangement is very convenient and widely used. Unfortunately it is also easy for unsupervised children to poison themselves by removing the unit dosages and ingesting them.
The invention seeks to render this kind of product more child resistant.
In U.S. Pat. No. 5,878,887 a blister card is received in a tray having a slidable cover. The cover has a tab with a locking projection that engages a slot in the tray. The pack can be partially opened by sliding the cover until the projection is at the end of the slot, and then flexing the tab upwardly to release the locking projection from the slot. This allows the cover to slide to an open position permitting access to the blister card.
In U.S. Pat. No. 5,473,371 a blister pack is folded in two and locked in the folded position by a locking member. To access the pack, the locking member is manually flexed to disengage a locking tab from the notches in the pack so that the locking member can be slidably disengaged from the pack. The pack can then be unfolded to provide access to the unit doses.
Providing a blister pack with a cover or sleeve that can be slidably removed only after releasing a locking mechanism reduces the risk of a child removing a unit dose without supervision. However the products described in the above US patents are generally complex and there is a need for a more reliable and robust childproof locking mechanism which does not add unduly to the cost of a blister pack and which is of a less complex design.
According to one aspect of the present invention there is provided a child-resistant unit dose holder comprising: a pack having a plurality of protrusions formed in a sheet, and a unit dose disposed in each of the protrusions; a sleeve for slidably receiving the pack, the sleeve covering the protrusions to prevent a unit dose being dispensed from the pack; and a releasable detent mechanism preventing slidable removal of the pack from the sleeve, at least one of the protrusions forming a detent of the detent mechanism.
By using one or more of the protrusions as a detent of the detent mechanism, a less complex and more reliable detent mechanism is provided.
According to another aspect of the present invention there is provided a child-resistant unit dose holder comprising: a pack having a plurality of protrusions formed in a sheet, each of the protrusions containing a unit dose and being spaced inwardly from opposed edges of the sheet; a sleeve for slidably receiving the pack, the sleeve comprising a flexible planar member having a pair of opposed inwardly extending flanges forming a slot for receiving the opposed edges of the strip, and a releasable detent mechanism preventing slidable removal of the pack from the sleeve, the detent mechanism being released in response to flexing of the planar member in a predetermined direction.